Use the same Rack version as the monolith

Gemfile.lock

@@ -66,6 +66,7 @@ PATH
   remote: gems/gitlab-safe_request_store
   specs:
     gitlab-safe_request_store (0.1.0)
+      rack (~> 2.2.8)
       request_store
 
 PATH

gems/gitlab-database-load_balancing/Gemfile.lock

@@ -16,6 +16,7 @@ PATH
   remote: ../gitlab-safe_request_store
   specs:
     gitlab-safe_request_store (0.1.0)
+      rack (~> 2.2.8)
       request_store
 
 PATH

gems/gitlab-safe_request_store/Gemfile.lock

@@ -2,6 +2,7 @@ PATH
   remote: .
   specs:
     gitlab-safe_request_store (0.1.0)
+      rack (~> 2.2.8)
       request_store
 
 GEM
@@ -35,7 +36,7 @@ GEM
       coderay (~> 1.1)
       method_source (~> 1.0)
     racc (1.6.2)
-    rack (3.0.4.1)
+    rack (2.2.8)
     rainbow (3.1.1)
     regexp_parser (2.7.0)
     request_store (1.5.1)

gems/gitlab-safe_request_store/gitlab-safe_request_store.gemspec

@@ -18,6 +18,7 @@ Gem::Specification.new do |spec|
   spec.files = Dir['lib/**/*.rb']
   spec.require_paths = ["lib"]
 
+  spec.add_runtime_dependency "rack", "~> 2.2.8"
   spec.add_runtime_dependency "request_store"
 
   spec.add_development_dependency "gitlab-styles", "~> 10.1.0"